Strange Spark Condition

[krisnowicki]

Boat sits in storage.... I pull it out and clean it, hook the hose up and it fires up, runs rough then once warm idles smooth.

Five mins later shuts off and spark is gone. Not able to restart it, frustrated I check spark with a timing light and its there on all cylinders. Gas is there, compression is 165 +/- 5 all around. So its spark.

I put it away. A week later it fires right up and repeats ....

Any ideas?

 

[krisnowicki]

Re: Strange Spark Condition

Thunderbolt V ignition

 

[Don S]

Re: Strange Spark Condition

Does your engine have a year? or a serial number?

Poor connction, failing ign. switch or kill switch just to name a few items.

 

[krisnowicki]

Re: Strange Spark Condition

I do not have the serials the ignition system is the newer kind, like those pictured here.

http://www.ebay.com/itm/350-MERCRUI..._Parts_Accessories_Gear&vxp=mtr#ht_500wt_1286

How can I test for a bad key switch? I have disconnected the tach.... no change.

Also, the kill switch is no in the loop

 

[Bondo]

Re: Strange Spark Condition

Five mins later shuts off and spark is gone. Not able to restart it, frustrated I check spark with a timing light and its there on all cylinders. Gas is there, compression is 165 +/- 5 all around. So its spark.

Ayuh,... Ya shoulda checked the spark plugs right then, 'n there....

If it was runnin' rough, it's probably over fueling...
If so, did it just flood out...
Gas fouled spark plugs, Don't spark....

A week later, they've dried...

 

[krisnowicki]

Re: Strange Spark Condition

it runs rich, noticably smell wise, when warming up. Maybe bad float then

 

[Don S]

Re: Strange Spark Condition

What year is the boat? the engine if changed? Is it the same ignition system as the original engine? I'm trying to figure out some wiring diagrams, but not getting much help from you.

 

[krisnowicki]

Re: Strange Spark Condition

Sorry don.

What year is the boat?
1988

the engine if changed?
Engine was a bravo repower from merc dealer, done in 2006 so although I dont have the serial I would imagine it is that vintage

Is it the same ignition system as the original engine?
when they did the repower everything was new, it came as a bobtail engine and they ran a new wire harness.

 

[krisnowicki]

Re: Strange Spark Condition

Started it tongiht, ran up for about a min and then shut it off, would not start again.

Quick question if I replace the ECM would I have to retime the engine, or would it start. I have a spare and am just trying to trouble shoot

 

[Don S]

Re: Strange Spark Condition

Started it tongiht, ran up for about a min and then shut it off, would not start again.

When it quit running, did you immediately check for spark? or power to the + terminal of the coil? That is 2 things you really MUST do if you want to fix your problem.

Did you shut it off, or did it die?

Quick question if I replace the ECM would I have to retime the engine, or would it start.

You don't have an ECM, that's only for EFI engines. and don't go throwing parts at it since you don't have a clue what is causing your problem.

 

[krisnowicki]

Re: Strange Spark Condition

when at all times I am having 12v at the coil. and yes spark was confirmed, so that leaves fuel?

Also, I jumped power to the fuel pump to see if I had a bad float or something causing a fuel leak out of the carb, when it running i se no droplets or anything.

I know I do not have an ECM but I mean the ignition control as I have an extra.

 

[krisnowicki]

Re: Strange Spark Condition

I turned it off... the only way to get it to even flutter was to pump the throttle a bunch

 

[Pete104]

Re: Strange Spark Condition

I'm leaning to carb issues. Not knowing exactly what engine, it's hard to tell what carburetor you have. But either Mercarb or the Weber are finiky with idle curcuits.

 

[krisnowicki]

Re: Strange Spark Condition

Also, when feathering the the throttle it will puff up through the carb....

 

[Bondo]

Re: Strange Spark Condition

Also, when feathering the the throttle it will puff up through the carb....

Ayuh,... Which indicates a Lean condition...

 

[CaptainKickback]

Re: Strange Spark Condition

Had a twin Merc I/O boat and one engine would just die unexpectedly. It would always restart sooner or later (usually 30 minutesvto several hours). My mechanic said it was a carb problem and comparing the cost of a carb to the cost of labor (at a marina), it was usually cheaper to replace the carb than troubleshoot it. Did so...problem gone

A year later, had the same problem on the other engine. Same fix, problem solved.

I'm not saying replace the carb. Just supporting some of the advice above.

 

[Don S]

Re: Strange Spark Condition

The next time it won't start, try this. Remove flame arrestor, pour about a shotglass full of gas into the carb, re-install the flame arrestor open the throttle about half throttle and see if it starts.

 

[krisnowicki]

Re: Strange Spark Condition

did that ... no change

 

[krisnowicki]

Re: Strange Spark Condition

tonights progress, pulled the carb .... it is clean no gun all passages good. Float seals, no leaks. There is gas.

Pulled the plugs, all are nice and dark/brown... good looking.

I put a timing light on the wires and I am getting eirraitc spark is the problem.

So it has to be a short?

 

[Don S]

Re: Strange Spark Condition

So it has to be a short?

A short what? Where? Tell us what you think a short is.